With common-rail systems, the system pressure in the rail is normally set by a pressure control valve. The pressure control valve guarantees a sufficiently accurate adjustability of the pressure during steady-state operation. During transient changes, a fast dynamic is required to enable a new operating state to be reached as quickly as possible and with the least possible deviations from the predetermined desired value.
With pressure control valves, the pressure in the rail can essentially be set by a magnetic force. For pressure regulation therefore, a PI controller with a pressure-dependent pilot control is used.
For reasons of stability, the speed at which a pressure regulation takes places is limited. A precise pilot control map is very important for achieving the minimum deviation from the desired pressure; the more exact this is the smaller the deviations of the desired pressure from the system pressure. The term “pilot control map” includes the term “pilot control characteristic curve”.
At present, the pilot control map is normally stored in a one-dimensional table. For adaptation it is first necessary to detect steady-first state operating conditions. If a steady-state operating condition lies in the vicinity of a support point of the table, it is used for adaptation of this point of the table.
Filtering non steady-state operating conditions and measurements that do not lie close to a support point results in a slow and inaccurate adaptation.